Epidermoid cysts presents as a nodular and fluctuant subcutaneous lesion beneath the skin and are most common in acne-prone areas of the head, neck and back. This cyst often arises after localized inflammation of the hair follicle and occasionally after the implantation of epithelium following trauma and surgery including a biopsy procedure. It is often associated with Gardner syndrome, particularly before puberty. The lesion is normally treated by a surgical excision or enucleation, and recurrence is uncommon. A 27 year old woman complained of a swelling of the left parotid gland when she visited our clinic. A cystic lesion was found in the left parotid gland from the high signal intensity on the MR images. Ultrasonography showed that the cystic lesion was heterogeneous echogenic. Six months earlier, botulinum toxin was injected in her left masseter muscles six months earlier and progressive swelling of the left parotid area was noticed four months after treatment. The lesion was surgically removed. It was encapsulated by a thin wall and filled mainly with keratin. The final diagnosis was an epidermoid cyst.